Synthesis and Rotational Isomerism of 1-Substituted Methyl (S)-[5-(2-Nitrophenyl)-1H-pyrazole-4-carbonyl]alaninates.

Seven title compounds 12a-g and the (S)-prolinate analogue 13 were prepared in five steps from 2-nitrobenzoic acid (7). Reduction of the nitro group followed by derivatization of the so formed anilines 14 gave the N-alkyl-(15a-c), N-acyl-(16a,b and 19), and N-vinyl derivative 20. NMR spectra of (S)-alanine and (S)-proline derived compounds 12, 13, 14-16, 19, and 20 exhibited two sets of signals corresponding to pairs of conformational diastereomers.

Isolation, analysis and structures of phototoxic fagopyrins from buckwheat.

Buckwheat products are commonly used in health foods and food supplements. However, public awareness regarding the presence of photodynamic naphthodianthrones fagopyrins that can cause photosensitization is low. At least two additional compounds with structures similar to that of fagopyrin are known to exist; however, the structures of these compounds have never been determined.